Some crude facts on oil refining

Because we are looking at $5-plus for gas and diesel this summer, I would like to know some specifics. When they talk about $100 a barrel, what size is the barrel: 55 gallons or 30 gallons or what? When this crude is refined, let's say this barrel is 55 gallons, does it produce 55 gallons of regular gas or 100 gallons? How about motor oil? I've been told that when producing regular gas the waste is diesel. Is that true or false? And are there refineries on the West Coast?

— R.A., Central Point

Well R.A., the process is a little more complicated than that.

First off, the barrels they talk about on the news are standardized at 42 gallons, but that's just a unit of measurement — the industry doesn't actually ship oil around in little 42-gallon barrels.

Second, only about 40 percent of the distilled crude comes off as gasoline, although that percentage can be increased by chemically processing the other byproducts of the distillation process. The refining process is a bit complicated, but here's a basic overview:

Crude contains a lot of hydrocarbons, which are molecules of hydrogen and carbon bound together into little molecular chains. There are many different types of hydrocarbon chains, depending on the length and the arrangement of molecules in the chain.

The crude is heated up to more than 1,000 degrees Celsius, separating the different hydrocarbon chains. Some chains are very short, such as propane, and separate quickly. Others are longer, such as diesel, and have a higher boiling point. Asphalt and tar are some of the longest and heaviest chains, only separating at more than 1,000 degrees Celsius.

Some of the separated hydrocarbon chains are ready to go after distillation, such as gasoline, but others have to go through further refinement before they're ready for use. Certain products from the distillation can be turned into other products as well by chemically breaking up the molecular chains or fusing shorter chains together.

All of the major oil companies have refineries on the West Coast, from Southern California to Puget Sound.

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